Re: [Qemu-devel] [PATCH 4/5] virtio-scsi: Add start/stop functionality for vhost-scsi

[Michael S. Tsirkin]

On Fri, Sep 14, 2012 at 08:45:11AM +0200, Paolo Bonzini wrote:
> Il 14/09/2012 00:27, Nicholas A. Bellinger ha scritto:
> > *) Keep vhost-scsi as a backend to virtio-scsi-pci
> > 
> >   - Reduces duplicated code amongst multiple virtio-scsi backends.
> >   
> >   - Follows the split for what existing vhost-net code already does.
> > 
> > So that said, two quick questions for Paolo & Co..
> > 
> > For the standalone vhost-scsi-pci device case, can you give a brief idea
> > as to what extent you'd like to see virtio-scsi.c code/defs duplicated
> > and/or shared amongst a new vhost-scsi-pci device..?
> 
> Not much, in the end, would be shared; it could end up being just
> parts of virtio_scsi_init and virtio_scsi_exit, and virtio_scsi_get_config.
> 
> Almost all the other code is to implement the SCSI bus interface,
> which you do not need.
> 
> I don't remember if and how vhost handles configuration changes.

All configuration changes are handled in userspace.

>  If you
> need any struct in virtio-scsi.c, either move it to virtio-scsi.h or
> add the new device in the same file.
> 
> > Also to help me along, can you give an example based on the current
> > usage below how the QEMU command line arguments would change with a
> > standalone vhost-scsi-pci device..?
> > 
> > ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -smp 4 -m 2048 \
> >     -hda /usr/src/qemu-vhost.git/debian_squeeze_amd64_standard-old.qcow2 \
> >     -vhost-scsi id=vhost-scsi0,wwpn=naa.600140579ad21088,tpgt=1 \
> >     -device virtio-scsi-pci,vhost-scsi=vhost-scsi0,event_idx=off
> 
> Two possibilities.  Either simply do s/virtio-scsi-pci/vhost-scsi-pci/ or do
> 
> ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -smp 4 -m 2048 \
>     -hda /usr/src/qemu-vhost.git/debian_squeeze_amd64_standard-old.qcow2 \
>     -device virtio-scsi-pci,wwpn=naa.600140579ad21088,tpgt=1,event_idx=off

I think I like the second option better.

-- 
MST